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[Xen-changelog] [xen-unstable] xen: add "lto=y" option to build Xen with

from [Xen patchbot-unstable] [Permanent Link][Original]
To: xen-changelog@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-changelog] [xen-unstable] xen: add "lto=y" option to build Xen with link-time optimizations.
From: Xen patchbot-unstable <patchbot@xxxxxxx>
Date: Thu, 10 Mar 2011 22:20:12 +0000
Delivery-date: Thu, 10 Mar 2011 14:24:45 -0800
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# HG changeset patch
# User Tim Deegan <Tim.Deegan@xxxxxxxxxx>
# Date 1299497649 0
# Node ID 076b63b74cf60b466aec379895a5ad348371fcb5
# Parent  d8ea33e7af7ee76ee3bea5411430ab876258ce78
xen: add "lto=y" option to build Xen with link-time optimizations.

This involves gathering object files from .asm (which will be binary)
and object files from .c (which will be in LTO format) separately
until the final link.

Only tested for x86_64 Xen builds using Clang/LLVM bitcode; it should be
possible to do the same with newer GCCs and GIMPLE.

Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Acked-by: Keir Fraser <keir@xxxxxxx>
---


diff -r d8ea33e7af7e -r 076b63b74cf6 config/StdGNU.mk
--- a/config/StdGNU.mk  Mon Mar 07 11:21:11 2011 +0000
+++ b/config/StdGNU.mk  Mon Mar 07 11:34:09 2011 +0000
@@ -1,10 +1,11 @@
 AS         = $(CROSS_COMPILE)as
+LD         = $(CROSS_COMPILE)ld
 ifeq ($(clang),y)
-LD         = $(CROSS_COMPILE)gold
 CC         = $(CROSS_COMPILE)clang
+LD_LTO     = $(CROSS_COMPILE)llvm-ld
 else
-LD         = $(CROSS_COMPILE)ld
 CC         = $(CROSS_COMPILE)gcc
+LD_LTO     = $(CROSS_COMPILE)ld
 endif
 CPP        = $(CC) -E
 AR         = $(CROSS_COMPILE)ar
@@ -79,3 +80,10 @@
 CFLAGS += -fno-optimize-sibling-calls
 endif
 endif
+
+ifeq ($(lto),y)
+CFLAGS += -flto
+ifeq ($(clang),y)
+LDFLAGS += -plugin LLVMgold.so
+endif
+endif
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/Makefile
--- a/xen/Makefile      Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/Makefile      Mon Mar 07 11:34:09 2011 +0000
@@ -159,4 +159,4 @@
        $(MAKE) -f $(BASEDIR)/Rules.mk -C $(*D) $(@F)
 
 %/: FORCE
-       $(MAKE) -f $(BASEDIR)/Rules.mk -C $* built_in.o
+       $(MAKE) -f $(BASEDIR)/Rules.mk -C $* built_in.o built_in_bin.o
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/Rules.mk
--- a/xen/Rules.mk      Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/Rules.mk      Mon Mar 07 11:34:09 2011 +0000
@@ -9,6 +9,8 @@
 lock_profile  ?= n
 crash_debug   ?= n
 frame_pointer ?= n
+clang         ?= n
+lto           ?= n
 
 XEN_ROOT=$(BASEDIR)/..
 include $(XEN_ROOT)/Config.mk
@@ -75,7 +77,8 @@
 
 # Most CFLAGS are safe for assembly files:
 #  -std=gnu{89,99} gets confused by #-prefixed end-of-line comments
-AFLAGS += $(AFLAGS-y) $(filter-out -std=gnu%,$(CFLAGS))
+#  -flto makes no sense and annoys clang
+AFLAGS += $(AFLAGS-y) $(filter-out -std=gnu%,$(filter-out -flto,$(CFLAGS)))
 
 # LDFLAGS are only passed directly to $(LD)
 LDFLAGS += $(LDFLAGS_DIRECT)
@@ -86,18 +89,45 @@
 subdir-n := $(patsubst %,%/,$(patsubst %/,%,$(subdir-n) $(subdir-)))
 subdir-y := $(patsubst %,%/,$(patsubst %/,%,$(subdir-y)))
 
-# Add explicitly declared subdirectories to the object list.
+# Add explicitly declared subdirectories to the object lists.
 obj-y += $(patsubst %/,%/built_in.o,$(subdir-y))
 
-# Add implicitly declared subdirectories (in the object list) to the
+# Add implicitly declared subdirectories (in the object lists) to the
 # subdirectory list, and rewrite the object-list entry.
 subdir-y += $(filter %/,$(obj-y))
 obj-y    := $(patsubst %/,%/built-in.o,$(obj-y))
 
 subdir-all := $(subdir-y) $(subdir-n)
 
+ifeq ($(lto),y)
+# Would like to handle all object files as bitcode, but objects made from
+# pure asm are in a different format and have to be collected separately.
+# Mirror the directory tree, collecting them as built_in_bin.o.
+# If there are no binary objects in a given directory, make a dummy .o
+obj-bin-y += $(patsubst %/built_in.o,%/built_in_bin.o,$(filter 
%/built_in.o,$(obj-y)))
+else
+# For a non-LTO build, bundle obj-bin targets in with the normal objs.
+obj-y += $(obj-bin-y)
+obj-bin-y :=
+endif
+
 built_in.o: $(obj-y)
+ifeq ($(obj-y),)
+       $(CC) $(CFLAGS) -c -x c /dev/null -o $@
+else
+ifeq ($(lto),y)
+       $(LD_LTO) -r -o $@ $^
+else
        $(LD) $(LDFLAGS) -r -o $@ $^
+endif
+endif
+
+built_in_bin.o: $(obj-bin-y)
+ifeq ($(obj-bin-y),)
+       $(CC) $(AFLAGS) -c -x assembler /dev/null -o $@
+else
+       $(LD) $(LDFLAGS) -r -o $@ $^
+endif
 
 # Force execution of pattern rules (for which PHONY cannot be directly used).
 .PHONY: FORCE
@@ -106,6 +136,9 @@
 %/built_in.o: FORCE
        $(MAKE) -f $(BASEDIR)/Rules.mk -C $* built_in.o
 
+%/built_in_bin.o: FORCE
+       $(MAKE) -f $(BASEDIR)/Rules.mk -C $* built_in_bin.o
+
 .PHONY: clean
 clean:: $(addprefix _clean_, $(subdir-all))
        rm -f *.o *~ core $(DEPS)
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/arch/x86/Makefile
--- a/xen/arch/x86/Makefile     Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/Makefile     Mon Mar 07 11:34:09 2011 +0000
@@ -10,8 +10,8 @@
 
 obj-y += apic.o
 obj-y += bitops.o
-obj-y += clear_page.o
-obj-y += copy_page.o
+obj-bin-y += clear_page.o
+obj-bin-y += copy_page.o
 obj-y += compat.o
 obj-y += debug.o
 obj-y += delay.o
@@ -65,24 +65,38 @@
        ./boot/mkelf32 $(TARGET)-syms $(TARGET) 0x100000 \
        `$(NM) -nr $(TARGET)-syms | head -n 1 | sed -e 's/^\([^ ]*\).*/0x\1/'`
 
+
 ALL_OBJS := $(BASEDIR)/arch/x86/boot/built_in.o $(ALL_OBJS)
 
-$(TARGET)-syms: $(ALL_OBJS) xen.lds
+ifeq ($(lto),y)
+# Gather all LTO objects together
+prelink_lto.o: $(ALL_OBJS)
+       $(LD_LTO) -r -o $@ $^
+
+# Link it with all the binary objects
+prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o
+       $(LD) $(LDFLAGS) -r -o $@ $^
+else
+prelink.o: $(ALL_OBJS)
+       $(LD) $(LDFLAGS) -r -o $@ $^
+endif
+
+$(TARGET)-syms: prelink.o xen.lds
        $(MAKE) -f $(BASEDIR)/Rules.mk $(BASEDIR)/common/symbols-dummy.o
-       $(LD) $(LDFLAGS) -T xen.lds -N $(ALL_OBJS) \
+       $(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
            $(BASEDIR)/common/symbols-dummy.o -o $(@D)/.$(@F).0
        $(NM) -n $(@D)/.$(@F).0 | $(BASEDIR)/tools/symbols >$(@D)/.$(@F).0.S
        $(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).0.o
-       $(LD) $(LDFLAGS) -T xen.lds -N $(ALL_OBJS) \
+       $(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
            $(@D)/.$(@F).0.o -o $(@D)/.$(@F).1
        $(NM) -n $(@D)/.$(@F).1 | $(BASEDIR)/tools/symbols >$(@D)/.$(@F).1.S
        $(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).1.o
-       $(LD) $(LDFLAGS) -T xen.lds -N $(ALL_OBJS) \
+       $(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
            $(@D)/.$(@F).1.o -o $@
        rm -f $(@D)/.$(@F).[0-9]*
 
 asm-offsets.s: $(TARGET_SUBARCH)/asm-offsets.c
-       $(CC) $(CFLAGS) -S -o $@ $<
+       $(CC) $(filter-out -flto,$(CFLAGS)) -S -o $@ $<
 
 xen.lds: xen.lds.S
        $(CC) -P -E -Ui386 $(AFLAGS) -o $@ $<
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/arch/x86/acpi/Makefile
--- a/xen/arch/x86/acpi/Makefile        Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/acpi/Makefile        Mon Mar 07 11:34:09 2011 +0000
@@ -1,4 +1,4 @@
 subdir-y += cpufreq
 
-obj-y += boot.o
-obj-y += power.o suspend.o wakeup_prot.o cpu_idle.o cpuidle_menu.o
+obj-y += boot.o power.o suspend.o cpu_idle.o cpuidle_menu.o
+obj-bin-y += wakeup_prot.o
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/arch/x86/boot/Makefile
--- a/xen/arch/x86/boot/Makefile        Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/boot/Makefile        Mon Mar 07 11:34:09 2011 +0000
@@ -1,4 +1,4 @@
-obj-y += head.o
+obj-bin-y += head.o
 
 head.o: reloc.S
 
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/arch/x86/boot/build32.mk
--- a/xen/arch/x86/boot/build32.mk      Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/boot/build32.mk      Mon Mar 07 11:34:09 2011 +0000
@@ -6,6 +6,7 @@
 $(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS))
 
 CFLAGS += -Werror -fno-builtin -msoft-float
+CFLAGS := $(filter-out -flto,$(CFLAGS)) 
 
 # NB. awk invocation is a portable alternative to 'head -n -1'
 %.S: %.bin
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/arch/x86/hvm/svm/Makefile
--- a/xen/arch/x86/hvm/svm/Makefile     Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/hvm/svm/Makefile     Mon Mar 07 11:34:09 2011 +0000
@@ -1,6 +1,6 @@
 obj-y += asid.o
 obj-y += emulate.o
-obj-y += entry.o
+obj-bin-y += entry.o
 obj-y += intr.o
 obj-y += svm.o
 obj-y += vmcb.o
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/arch/x86/hvm/vmx/Makefile
--- a/xen/arch/x86/hvm/vmx/Makefile     Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/hvm/vmx/Makefile     Mon Mar 07 11:34:09 2011 +0000
@@ -1,4 +1,4 @@
-obj-y += entry.o
+obj-bin-y += entry.o
 obj-y += intr.o
 obj-y += realmode.o
 obj-y += vmcs.o
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/arch/x86/x86_32/Makefile
--- a/xen/arch/x86/x86_32/Makefile      Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/x86_32/Makefile      Mon Mar 07 11:34:09 2011 +0000
@@ -1,6 +1,6 @@
 obj-y += domain_page.o
-obj-y += entry.o
-obj-y += gpr_switch.o
+obj-bin-y += entry.o
+obj-bin-y += gpr_switch.o
 obj-y += mm.o
 obj-y += seg_fixup.o
 obj-y += traps.o
@@ -9,4 +9,4 @@
 
 obj-$(crash_debug) += gdbstub.o
 
-obj-$(supervisor_mode_kernel) += supervisor_mode_kernel.o
+obj-bin-$(supervisor_mode_kernel) += supervisor_mode_kernel.o
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/arch/x86/x86_64/Makefile
--- a/xen/arch/x86/x86_64/Makefile      Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/x86_64/Makefile      Mon Mar 07 11:34:09 2011 +0000
@@ -1,7 +1,7 @@
 subdir-y += compat
 
-obj-y += entry.o
-obj-y += gpr_switch.o
+obj-bin-y += entry.o
+obj-bin-y += gpr_switch.o
 obj-y += mm.o
 obj-y += traps.o
 obj-y += machine_kexec.o
@@ -11,7 +11,7 @@
 obj-y += mmconfig_64.o
 obj-y += mmconfig-shared.o
 obj-y += compat.o
-obj-y += compat_kexec.o
+obj-bin-y += compat_kexec.o
 obj-y += domain.o
 obj-y += physdev.o
 obj-y += platform_hypercall.o
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/arch/x86/x86_64/compat/Makefile
--- a/xen/arch/x86/x86_64/compat/Makefile       Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/x86_64/compat/Makefile       Mon Mar 07 11:34:09 2011 +0000
@@ -1,2 +1,2 @@
-obj-y += entry.o
+obj-bin-y += entry.o
 
diff -r d8ea33e7af7e -r 076b63b74cf6 xen/common/libelf/Makefile
--- a/xen/common/libelf/Makefile        Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/common/libelf/Makefile        Mon Mar 07 11:34:09 2011 +0000
@@ -1,4 +1,4 @@
-obj-y := libelf.o
+obj-bin-y := libelf.o
 
 SECTIONS := text data rodata $(foreach n,1 2 4 8,rodata.str1.$(n)) $(foreach 
r,rel rel.ro,data.$(r) data.$(r).local)
 

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